Normal results for a gastric emptying study are defined by how much of a standardized meal remains in your stomach at set time points over four hours. Using the widely accepted egg-white meal protocol, the key benchmark is the four-hour mark: retaining 10 percent or less of the meal is considered normal. At one hour, up to about 90 percent retention is typical, and at two hours, up to about 60 percent. Those cutoffs come from a multicenter study that underpins the joint consensus guidelines used by most nuclear medicine departments in North America, but what counts as “normal” turns out to depend on more variables than that simple set of numbers suggests.
How the Test Is Done
A gastric emptying scintigraphy study, often just called a GES, involves eating a meal that has been mixed with a tiny amount of a radioactive tracer, usually technetium-99m sulfur colloid. The standard meal recommended by the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine is a low-fat, egg-white sandwich with toast and jam, plus water. After you eat, a gamma camera takes images of your abdomen at specific intervals, typically at 0, 1, 2, and 4 hours after meal ingestion.1PubMed. Consensus recommendations for gastric emptying scintigraphy: a joint report of the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine Some centers also image at half-hour intervals for additional detail.2PubMed. Optimal timing of imaging in gastric emptying scintigraphy for the detection of delayed emptying
The camera captures images from both the front and back of your body. That dual-view approach matters because the stomach sits at an angle inside the abdomen, and as food shifts from the back part of the stomach toward the front, it can look like there is more radioactivity than there really is if you only image from one direction. The standard correction for this uses a geometric mean calculation that combines both views to give an accurate count of how much meal is still inside the stomach.3Journal of Neurogastroenterology and Motility. How to Interpret Gastric Emptying Scintigraphy Without that correction, errors in the measurement can be significant.4PubMed. Correction for tissue attenuation in radionuclide gastric emptying studies: a comparison of a lateral image method and a geometric mean method
The Numbers That Define Normal
Results are reported as a percentage of gastric retention at each imaging time point. The consensus-derived normal values for the standard egg-white meal are:
- 1 hour: up to about 90 percent retention
- 2 hours: up to about 60 percent retention
- 4 hours: up to 10 percent retention
A study of 24 healthy volunteers eating the full standard sandwich found mean retention of about 75 percent at one hour, roughly 31 percent at two hours, and about 2 percent at four hours.5PubMed Central. Normal Gastric Emptying Scintigraphy Values for Limited Meal Ingestion Those are averages in healthy people, so the normal range has a comfortable margin above them. The four-hour number is the single most important checkpoint; if you still have more than 10 percent of the meal in your stomach at four hours, the study is classified as showing delayed gastric emptying.
The two-hour value provides supporting context. If more than 60 percent of the meal remains at two hours, that also flags a delay, even before you reach the four-hour mark. Some researchers and clinicians find the two-hour measurement useful for grading severity or for catching a trend when a patient cannot complete the full four-hour study, although the four-hour endpoint remains the gold standard for diagnosis.
When Emptying Is Delayed
Delayed gastric emptying, the hallmark of gastroparesis, is formally defined as greater than 10 percent retention at four hours or greater than 60 percent at two hours using the standard meal. In clinical practice, doctors sometimes break delayed emptying into severity grades: mild (11–20 percent retained at four hours), moderate (21–35 percent), and severe (36 percent or more). These grades help guide treatment decisions, though they are somewhat arbitrary and not universally applied the same way across all centers.
An important caveat: the degree of delay on the scan does not reliably predict how bad a patient’s symptoms will be. Multiple studies have found that symptom severity in functional dyspepsia and suspected gastroparesis does not correlate well with the measured gastric emptying rate.6PubMed. Relationship Between Gastric Emptying Rate and Simultaneously Assessed Symptoms in Functional Dyspepsia One study found that patients with delayed and normal emptying had essentially the same symptom profiles during the test, suggesting that factors like impaired gastric accommodation, the stomach’s ability to relax and expand after a meal, may matter more for explaining symptoms than the emptying rate itself.7PubMed Central. Postprandial symptoms in patients with symptoms of gastroparesis: roles of gastric emptying and accommodation If your scan shows borderline-delayed emptying but you feel terrible, or your scan shows a clear delay but your symptoms are mild, neither result is unusual.
When Emptying Is Too Fast
Gastric emptying studies can also detect the opposite problem: rapid gastric emptying, sometimes called dumping. The diagnostic threshold used in research is more than 50 percent of the meal emptied at one hour, which means less than 50 percent retention on the scan at the one-hour image.8PubMed. Dumping syndrome: establishing criteria for diagnosis and identifying new etiologies Rapid emptying is most associated with prior stomach surgery, but it can also occur in people with diabetes, functional dyspepsia, and cyclic vomiting syndrome. When food dumps into the small intestine too quickly, it can trigger nausea, cramping, diarrhea, dizziness, and sweating shortly after eating.
Rapid emptying is often underdiagnosed because the test is usually ordered with delayed emptying in mind, and the one-hour image may not receive as much attention if the referring physician’s main concern is gastroparesis. If your symptoms happen right after eating rather than an hour or two later, it is worth asking whether rapid emptying was specifically evaluated on the scan.
Preparation Makes or Breaks Accuracy
A gastric emptying study is only as reliable as the preparation that precedes it. The standard procedure guideline calls for nothing by mouth for at least four hours before the test, ideally fasting from midnight if the study is done in the morning.9Journal of Nuclear Medicine Technology. Procedure Guideline for Adult Solid-Meal Gastric-Emptying Study 3.0 You need to eat the entire test meal within about 10 minutes, and smoking, gum chewing, and vigorous activity during the study should be avoided since all of these can alter motility.
For women who are premenopausal, the ideal window is the first 10 days of the menstrual cycle, because hormonal fluctuations later in the cycle can slow gastric emptying and potentially push a normal result into the delayed range.9Journal of Nuclear Medicine Technology. Procedure Guideline for Adult Solid-Meal Gastric-Emptying Study 3.0 In practice, not all scheduling departments account for this, so it is something you can raise proactively.
If you have diabetes, blood sugar at the time of the meal matters. Even mild hyperglycemia, at levels around 144 mg/dL, can slow gastric emptying in people with type 1 diabetes.10PubMed Central. Relationship Between Control of Glycemia and Gastric Emptying Disturbances in Diabetes Mellitus The guideline recommends recording blood sugar at the time of meal ingestion and ideally having it below 200 mg/dL. Bring your glucose monitor and insulin to the appointment, and plan ahead with your doctor about adjusting your morning insulin dose for the test meal.9Journal of Nuclear Medicine Technology. Procedure Guideline for Adult Solid-Meal Gastric-Emptying Study 3.0
Medications That Throw Off the Results
Several medication classes can distort gastric emptying enough to produce a false result. Opioid pain medications and anticholinergic drugs are the classic offenders; both slow the stomach and could make it look like you have gastroparesis when you do not. The consensus guidelines recommend stopping these at least two days before the test.11Journal of Nuclear Medicine Technology. Consensus Recommendations for Gastric Emptying Scintigraphy: A Joint Report of the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine Prokinetic medications like metoclopramide and erythromycin, which speed up the stomach, should also be held for the same period unless the whole point of the test is to evaluate whether those drugs are working.
GLP-1 receptor agonists, the class that includes semaglutide and liraglutide, have become a particularly relevant issue. These drugs, widely prescribed for type 2 diabetes and weight management, slow gastric emptying as part of their mechanism. A meta-analysis found that patients on GLP-1 agonists had a mean gastric half-emptying time about 36 minutes longer than those on placebo.12PubMed Central. Quantified Metrics of Gastric Emptying Delay by GLP-1 Agonists: A Systematic Review and Meta-Analysis with Insights for Periprocedural Management One study with liraglutide showed a 23 percent decrease in gastric emptying at the one-hour mark for the higher dose, compared to placebo.13PubMed Central. GLP-1 receptor agonists and delayed gastric emptying: implications for invasive cardiac interventions and surgery
The practical dilemma is this: if you take a GLP-1 agonist and have gastroparesis symptoms, the test cannot tell whether your delayed emptying is caused by diabetic neuropathy affecting the stomach or by the medication itself. A normal GES result while on the drug does rule out both causes, which is useful. But a delayed result is ambiguous.14Journal of Nuclear Medicine Technology. Glucagonlike Peptide-1 Receptor Agonists: The Good, the Bad, and the Ugly—Benefits for Glucose Control and Weight Loss with Side Effects of Delaying Gastric Emptying There is no universally agreed-upon washout period for GLP-1 agonists before testing, partly because their long half-lives and variable effects make it complicated. If you are on one of these medications and your doctor orders a GES, it is worth having a direct conversation about whether to pause the drug and for how long.
Sex Differences in Normal Emptying
Women generally empty their stomachs more slowly than men. One study of healthy volunteers found that the time-to-peak emptying rate was about 54 minutes in women versus 43 minutes in men, a statistically significant difference that led the researchers to propose separate diagnostic cutoffs by sex.15Digestion. Gender Difference of Gastric Emptying in Healthy Volunteers and Patients with Functional Dyspepsia Despite this evidence, most clinical labs in the United States still use the same reference ranges for everyone. The consensus guidelines do not incorporate sex-specific cutoffs. The result is that some women with genuinely normal emptying may fall just outside the universal thresholds, and clinicians should consider this when interpreting borderline results.
Age may also play a role, though the evidence is less consistent. Older adults tend to empty somewhat more slowly, but the effect is smaller than the sex difference and has not led to separate age-based reference ranges in clinical practice.
What Happens When the Meal Isn’t Standard
The reference values described above apply specifically to the standardized egg-white meal. Change the meal, and the numbers change. This matters because not every patient can eat the standard meal. Egg allergies, vegan diets, and cultural food preferences have prompted centers to explore alternatives. The problem is that each substitute empties at its own pace, so the standard thresholds may not apply.
EnsurePlus, a commonly used liquid nutritional supplement, has been studied as a substitute. It showed similar retention to the egg meal at one and two hours, but significantly higher retention at three and four hours.16PubMed. EnsurePlus as an Alternative to the Standardized Egg Gastric-Emptying Meal That means using the standard egg-meal cutoffs to interpret an EnsurePlus study could overdiagnose delayed emptying. Researchers have proposed separate reference limits for EnsurePlus, with the upper end of normal at about 14 percent retention at four hours instead of 10 percent.
Trials comparing an Asian-style liquid meal (Vital) to the egg-white meal found that the liquid meal emptied considerably faster at most time points, with comparable results only at the four-hour mark.17PubMed. Randomized, crossover trial: comparing the effects of standardized egg-white meal and Vital on global gastric emptying parameters and intragastric meal distribution in healthy Asian participants A separate Asian multicenter study using a rice-based solid meal found a median gastric half-emptying time of about 69 minutes and median retention of roughly 16 percent at two hours and just 1 percent at four hours in healthy volunteers.18PubMed Central. Normal Solid Gastric Emptying Values Measured by Scintigraphy Using Asian-style Meal: A Multicenter Study in Healthy Volunteers These values look different from the egg-meal norms, reinforcing that meal composition and local reference ranges go hand in hand.
Meal size matters too. When healthy subjects ate a half-size or quarter-size version of the standard sandwich, retention at one and two hours was significantly lower than with the full meal, even though the four-hour values converged.5PubMed Central. Normal Gastric Emptying Scintigraphy Values for Limited Meal Ingestion If a patient cannot finish the full meal, the early time-point values need to be interpreted differently. Some labs will note the percentage of the meal consumed on the report; if yours does not, ask.
Solid Food Versus Liquid
Most standard gastric emptying studies measure solid emptying only, but some clinicians order a combined solid-and-liquid test. The stomach handles liquids and solids through different mechanisms. Solid food is ground down in the antrum to particles about 1–2 mm in size before passing through the pylorus, a process driven by strong muscular contractions.19PubMed Central. Gastrointestinal Hormones and Regulation of Gastric Emptying Liquids bypass much of that process and can empty independently.
This distinction has clinical consequences. One study found that among patients with normal solid emptying, a third had delayed liquid emptying.20PubMed. Liquid gastric emptying is often abnormal when solid emptying is normal If you have symptoms like nausea or early fullness and your solid-only study comes back normal, a combined study or a dedicated liquid-phase study may reveal a problem that was missed. This is something to discuss with your gastroenterologist, particularly if your symptoms are predominantly with liquids or if the solid-only result seems at odds with how you feel.
Alternatives to the Scintigraphy Scan
The gamma-camera scintigraphy study remains the most widely used and validated test for gastric emptying, but two alternatives exist for situations where scintigraphy is unavailable or impractical.
A stable-isotope breath test uses a meal labeled with carbon-13 (a non-radioactive isotope) and measures how quickly the label appears in your exhaled breath as an indirect gauge of emptying speed. The correlation with scintigraphy is strong. One validation study found a concordance correlation coefficient of 0.95 between the breath test and scintigraphic measurements across all subjects.21PubMed Central. Comprehensive Assessment of Gastric Emptying with a Stable Isotope Breath Test Another study showed that even a simplified three-sample breath protocol predicted emptying half-time values comparable to scintigraphy, with a standard deviation of difference of only 10 minutes.22Gut. A valid, accurate, office based non-radioactive test for gastric emptying of solids The breath test can be done in a regular office setting and involves no radiation, which makes it appealing for repeat testing, pediatric use, or pregnant patients.
The wireless motility capsule is a small, swallowable device that records pH, pressure, and temperature as it travels through the entire digestive tract. It can measure gastric emptying by detecting the sharp pH change that occurs when it passes from the acidic stomach into the alkaline small intestine. Clinical trials have shown it to be a suitable alternative to scintigraphy for measuring gastric emptying.23PubMed Central. A technical review and clinical assessment of the wireless motility capsule A bonus is that it also gives transit data for the small bowel and colon in the same test, which can be helpful when the clinical picture involves more than just the stomach.
Radiation Exposure
Because the standard test uses a radioactive tracer, patients reasonably ask about radiation risk. The amount of technetium-99m used is small, typically around 0.5 to 1 millicurie. At these doses, the effective radiation dose works out to roughly 0.2 to 0.5 millisieverts, which is a fraction of the annual background radiation you absorb from natural sources and comparable to a single chest X-ray or less. The tracer decays with a half-life of about six hours and is not absorbed from the gut into your bloodstream, so systemic exposure is minimal. For most adults, the radiation from one gastric emptying study is clinically trivial, though the test is generally avoided in pregnancy when alternatives like the breath test are available.